1. Field of the Invention
The present invention relates generally to a fiber optic penetrator for allowing fiber optic communication lines to penetrate through the wall of an undersea apparatus employed in the exploration and production of offshore oil wells, and which is subjected to a very high pressure differential thereacross.
2. Discussion of the Prior Art
The state of the art discloses several different types of penetrators for effecting signal communications through a bulkhead or wall structure separating physical environments of significantly different pressure, and more particularly, penetrators for conveying optical fibers of fiber optic communication systems therethrough. Redfern U.S. Pat. No. 3,825,320, Allard U.S. Pat. No. 3,951,515, Heinzer U.S. Pat. No. 4,172,212 and Reh U.S. Pat. No. 4,214,809 all disclose various embodiments of penetrators. The term bulkhead is used generically herein to cover the wall or partition structures of undersea apparatus employed in offshore oil well exploration and production.
Fiber optic communication systems offer a number of distinct advantages in offshore environments, such as apparatus employed for oil well exploration and production, relative to traditional electrical cable communication systems. One problem with transmitting information through standard electrical cables is the undesirable effect of radiated and conducted electromagnetic interference normally associated with these cables. Such interference may, for example, cause spurious or other erroneous readings from equipment attached to the cable. The advantages to be gained by an optical communication system over the use of conventional wire cables include higher per channel data rate capability, immunity to electromagnetic interference, lower cable weight, elimination of fire hazard due to electrical shorting, and potentially lower cost. For some data link applications, multi-fiber bundles of medium and high loss fiber are utilized. Light emitting diodes (LEDs) are frequently employed as optical sources, and photodiodes are often used for optical detection.
In optic fiber communication systems, the requirements for a penetrator are, in some respects, more severe than for electric systems using metallic conductors and, in other respects, less severe, since the optic fibers are not subject to shorting by conductive sea water. Fiber optic penetrators preferably should not involve interruption of the light path by interface structures, since these are inevitably, at least somewhat, lossy.